The study aimed to assess the severity of fatigue in patients with axial spondyloarthritis (AxSpA), to assess the performance of two different fatigue measures in AxSpA, and to examine disease variables which may influence the severity of fatigue. Fatigue was examined among 67 patients with AxSpA using two measures: the fatigue Visual Analogue Scale (VAS) from the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Multidimensional Assessment of Fatigue (MAF) score. These measures were tested for convergent validity using linear regression analysis. Correlations between fatigue measured using both questionnaires, and key disease variables was examined using the following assessments: BASDAI, Bath Ankylosing Spondylitis Functional Index (BASFI), Ankylosing Spondylitis Quality of Life (ASQoL) questionnaire, spondyloarthritis modification of the Dudley Inflammatory Bowel Symptom Questionnaire (DISQ) and pain VAS. Human leucocyte antigen (HLA) B27 and CRP were performed and followed by physical examination, Bath AS Metrology Index (BASMI) and Ankylosing Spondylitis Disease Activity Score (ASDAS). Correlations were assessed using multivariate regression analysis. Mean (±SD) fatigue measured by MAF (range 0-50) was 24.7 (±11.5) and 5.14 (±2.47) on the BASDAI VAS fatigue item (range 0-10). The MAF scores and BASDAI VAS fatigue were strongly correlated (r = 0.71, P < 0.001), but 50 % of variance remained unexplained, so both were retained as separate variables in bivariate and multivariate analyses. In multivariate regression models, a significant relationship for both fatigue measures was consistently noted with DISQ bowel symptom scores. MAF fatigue scores were most strongly associated with poorer ASQoL in multivariate models and mediated the effects of BASFI functioning, ASDAS disease activity and HLA-B27 status that were apparent in multivariate models. Patients with AxSpA experience substantial fatigue, which is associated with poorer quality of life. Fatigue VAS and MAF scores were strongly correlated. Factors most strongly associated with fatigue were disease activity and inflammatory bowel symptoms.